Allow backspace to wrap cursor to previous line

Fixes #8841

kitty_tests/graphics.py

@@ -766,7 +766,7 @@ class TestGraphics(BaseTest):
         s.draw("\U0010EEEE\u0305\u0305\U0010EEEE\u0305\u030D")
         # These two characters will be two separate refs (not contiguous).
         s.draw("\U0010EEEE\u0305\u0305\U0010EEEE\u0305\u030E")
-        s.cursor_back(4)
+        s.cursor_move(4)
         s.update_only_line_graphics_data()
         refs = layers(s)
         self.ae(len(refs), 3)
@@ -786,7 +786,7 @@ class TestGraphics(BaseTest):
         # The second image, 2x1
         s.apply_sgr("38;2;42;43;44")
         s.draw("\U0010EEEE\u0305\u030D\U0010EEEE\u0305\u030E")
-        s.cursor_back(2)
+        s.cursor_move(2)
         s.update_only_line_graphics_data()
         refs = layers(s)
         self.ae(len(refs), 2)
@@ -804,7 +804,7 @@ class TestGraphics(BaseTest):
         s.draw("\U0010EEEE\u0305\u0305\U0010EEEE\u0305\U0010EEEE\U0010EEEE\u0305")
         # full row 1 of the first image
         s.draw("\U0010EEEE\u030D\U0010EEEE\U0010EEEE\U0010EEEE\u030D\u0310")
-        s.cursor_back(8)
+        s.cursor_move(8)
         s.update_only_line_graphics_data()
         refs = layers(s)
         self.ae(len(refs), 2)
@@ -826,7 +826,7 @@ class TestGraphics(BaseTest):
         # This one will have id=43, which does not exist.
         s.apply_sgr("38;2;0;0;43")
         s.draw("\U0010EEEE\u0305\U0010EEEE\U0010EEEE\U0010EEEE")
-        s.cursor_back(4)
+        s.cursor_move(4)
         s.update_only_line_graphics_data()
         refs = layers(s)
         self.ae(len(refs), 0)
@@ -842,7 +842,7 @@ class TestGraphics(BaseTest):
         s.draw("\U0010EEEE\u0305\u0305\u059C\U0010EEEE\u0305\u030D\u059C")
         # Check that we can continue by using implicit row/column specification.
         s.draw("\U0010EEEE\u0305\U0010EEEE")
-        s.cursor_back(6)
+        s.cursor_move(6)
         s.update_only_line_graphics_data()
         refs = layers(s)
         self.ae(len(refs), 2)
@@ -856,7 +856,7 @@ class TestGraphics(BaseTest):
         s.draw("\U0010EEEE\u0305\u0305\u0305\U0010EEEE")
         s.apply_sgr("38;5;43")
         s.draw("\U0010EEEE\u0305\u0305\u059C\U0010EEEE\U0010EEEE\u0305\U0010EEEE")
-        s.cursor_back(6)
+        s.cursor_move(6)
         s.update_only_line_graphics_data()
         refs = layers(s)
         self.ae(len(refs), 2)

kitty_tests/parser.py

@@ -353,7 +353,7 @@ class TestParser(BaseTest):
         s = self.create_screen()
         pb = partial(self.parse_bytes_dump, s)
         pb('abcde', 'abcde')
-        s.cursor_back(5)
+        s.cursor_move(5)
         pb('x\033[2@y', 'x', ('screen_insert_characters', 2), 'y')
         self.ae(str(s.line(0)), 'xy bc')
         pb('x\033[2;7@y', 'x', ('CSI code @ has 2 > 1 parameters',), 'y')

kitty_tests/screen.py

@@ -44,7 +44,7 @@ class TestScreen(BaseTest):
         s.reset(), s.reset_dirty()
         s.set_mode(IRM)
         s.draw('12345' * 5)
-        s.cursor_back(5)
+        s.cursor_move(5)
         self.ae(s.cursor.x, 0), self.ae(s.cursor.y, 4)
         s.reset_dirty()
         s.draw('ab')
@@ -98,7 +98,7 @@ class TestScreen(BaseTest):
         s.set_mode(IRM)
         s.draw(text * 5)
         self.ae(str(s.line(0)), text)
-        s.cursor_back(5)
+        s.cursor_move(5)
         self.ae(s.cursor.x, 0), self.ae(s.cursor.y, 4)
         s.reset_dirty()
         s.draw('a\u0306b')
@@ -162,7 +162,7 @@ class TestScreen(BaseTest):
             s.reset(), s.reset_dirty()
             s.draw('abcde')
             s.cursor.bold = True
-            s.cursor_back(4)
+            s.cursor_move(4)
             s.reset_dirty()
             self.ae(s.cursor.x, 1)
 
@@ -170,11 +170,11 @@ class TestScreen(BaseTest):
         s.insert_characters(2)
         self.ae(str(s.line(0)), 'a  bc')
         self.assertTrue(s.line(0).cursor_from(1).bold)
-        s.cursor_back(1)
+        s.cursor_move(1)
         s.insert_characters(20)
         self.ae(str(s.line(0)), '')
         s.draw('xココ')
-        s.cursor_back(5)
+        s.cursor_move(5)
         s.reset_dirty()
         s.insert_characters(1)
         self.ae(str(s.line(0)), ' xコ')
@@ -270,7 +270,7 @@ class TestScreen(BaseTest):
         self.ae((s.cursor.x, s.cursor.y), (0, 1))
         s.cursor_forward(3)
         self.ae((s.cursor.x, s.cursor.y), (3, 1))
-        s.cursor_back()
+        s.cursor_move()
         self.ae((s.cursor.x, s.cursor.y), (2, 1))
         s.cursor_down()
         self.ae((s.cursor.x, s.cursor.y), (2, 2))
@@ -534,6 +534,28 @@ class TestScreen(BaseTest):
         s.draw('aaaX\tbbbb')
         self.ae(str(s.line(0)) + str(s.line(1)), 'aaaXbbbb')
 
+    def test_backspace(self):
+        s = self.create_screen()
+        q = 'a'*s.columns
+        def backspace(use_bs=True):
+            if use_bs:  # this is how the kernel implements backspace
+                s.draw('\x08 \x08')
+            else:
+                s.cursor_move(1)
+                s.draw(' ')
+                s.cursor_move(1)
+        for use_bs in (True, False):
+            s.reset()
+            s.draw(q)
+            s.draw('b')
+            backspace(use_bs)
+            self.ae(str(s.line(0)), q)
+            self.ae(str(s.line(1)), ' ')
+            self.ae(s.cursor.x, 0)
+            backspace(use_bs)
+            self.ae(str(s.line(0)), q[:-1] + ' ')
+            self.ae(str(s.line(1)), ' ')
+
     def test_margins(self):
         # Taken from vttest/main.c
         s = self.create_screen(cols=80, lines=24)